Page 603 - The Veterinary Laboratory and Field Manual 3rd Edition

appendix 5

Colibacillosis in poultry: example

with diagnostic flowchart

Karen Liljebjelke

Escherichia coli is a ubiquitous bacteria present O18 and O78. The serotypes O1, O2 and O78
in many environments. It is an opportunis- account for up to 70% of APEC infections in
tic bacterium in poultry, usually secondary to poultry. Sero-grouping allows for identifica-
other diseases, such as infectious bronchitis, tion of a limited number of APEC strains, but
mycoplasma or management problems which will identify the six most common serogroups
predispose the birds to infection. Colibacillosis isolated from lesions. Sero-grouping is not nec-
is a major cause of morbidity and mortality in essary to make a diagnosis of colibacillosis. If
poultry, and causes significant economic losses the blood sample or swab sample is carefully col-
worldwide. Avian pathogenic E. coli (APEC) lected from a freshly dead or recently euthanized
infection causes a variety of syndromes in poul- carcass with lesions consistent with E. coli infec-
try, including airsacculitis, colisepticaemia, tion, the isolation of pure E. coli is supportive of
cellulitis, arthritis, salpingitis and peritonitis in a diagnosis of colibacillosis.
poults and laying hens, and omphalitis and yolk Autogenous vaccines can be used to immunize
sac infection in chicks. a laying flock. The vaccine will reduce mortality,
E. coli infection leads to increased mortality but may not reduce morbidity or the drop in egg
in laying hens with obvious lesions in the peri- production. It can take weeks to match the field
cardium, liver, spleen and air sacs. A drop in egg strain and produce an autogenous vaccine. In
production may or may not occur in the flock. addition, handling and vaccination of each indi-
Free range, colony cage or cage-free housing sys- vidual bird may be prohibitively time and labour
tems are challenging to manage and may increase expensive.
spread of infection with APEC. There are limited
options for control of E. coli infections during
the laying period because there are few antibiot- diagnostic scheme for E. coli
ics approved for use during lay that have zero
withdrawal time for eggs. Extra-label use of anti- 1 Use sterile technique to collect a swab sam-
biotics will result in residues in the eggs. ple from fresh post-mortem tissue lesions.
Bacteriological testing (see Figure A5.1) Alternately, a fresh blood sample from an
will confirm the presence of APEC. There are affected bird may be used.
six strains of E. coli that are most commonly 2 Streak the swab sample onto MacConkey
associated with avian disease: O1, O2, O5, O8, agar and incubate at 37°C for 18–24 h. If

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